The prevalence of problem behaviors increases dramatically during adolescence. Problem behaviors such as school misconduct, underachievement, and dropout; tobacco, alcohol, and other drug use; violence and delinquency place youth at an increased risk for school failure, involvement in the criminal justice system, and chronic substance abuse. This study is an efficacy trial of school-based interventions designed to improve students' social competence and develop supportive social environments, thereby reducing the prevalence of problem behavior among middle school students.